1. Field of the Invention
The present invention relates to a wireless local access network (WLAN), and more particularly, to a direct link setup procedure in a tunneled direct link setup (TDLS) wireless network and a station supporting the direct link setup procedure.
2. Related Art
With the development of information communication technology, a variety of wireless communication technology has been developed. A wireless LAN (WLAN) is a technique permitting wireless access to its local network or Internet in specific service areas such as home or companies or air planes by the use of portable terminals such as a personal digital assistant (PDA), a laptop computer, and a portable multimedia player (PMP) on the basis of the radio communication technology.
These days, thanks to the increased availability of WLANs, portable terminal users such as laptop computer users are able to perform their tasks with increased mobility. For example, a user can take his laptop computer from his desk into a conference room to attend a meeting and still have access to his local network to retrieve data and have access to the Internet via one or more modems or gateways present on the local network without being tethered by a wired connection. Similarly, business travelers commonly use their portable terminals to gain access to their email accounts, to check if there is any unread email, and to read and send email.
In the initial WLAN technology, a data rate of 1 to 2 Mbps was supported by the use of frequency hopping, spread spectrum, and infrared communication using a frequency of 2.4 GHz. In recent years, with the development of the wireless communication technology, 54 Mbps in maximum can be supported by applying the Orthogonal Frequency Division Multiplex (OFDM) technology, etc. to the WLAN. In addition, the IEEE 802.11 has developed or is developing wireless communication technologies for improvement in quality of service (QoS), compatibility of an access point (AP) protocol, security enhancement, wireless resource measurement, wireless access in vehicular environment, fast roaming, mesh network, inter-working with external networks, wireless network management, and the like.
In the IEEE 802.11, a Basic Service Set (BSS) means a set of stations (STAs) successfully synchronized. A Basic Service Area (BSA) means an area including members of the BSS. The BSA can vary depending on propagation characteristics of a wireless medium and thus it may contain members of other basic service sets.
The BSS can be basically classified into two kinds of an independent BSS (IBSS) and an infra-structured BSS. The former means a BSS that constitutes a self-contained network and that is not permitted to access a Distribution System (DS). The latter means a BSS that includes one or more Access Points (APs) and a distribution system and that uses the APs in all the communication processes including communications between the Non-AP stations.
In the initial WLAN communication procedure, it was required that data is necessarily transmitted through the AP in the infra-structured BSS. That is, the direct transmission of data between non-AP stations (non-AP STAs) is not allowed in the infra-structured BSS. In recent years, a direct link setup (DLS) between the non-AP STAs supporting Quality of Service (QoS) has been introduced to improve the efficiency of wireless communications. Accordingly, in the BSS supporting the QoS, that is, in the QBSS including QoS STAs (QSTA) and QoS APs (QAP), the non-AP STAs can set up a direct link therebetween and directly communicate with each other through the direct link.
As described above, the existing DLS setup method is based on the premise that the BSS is the QBSS, which is a BSS supporting the QoS. In the QBSS, the AP as well as the non-AP STA is a QAP, which is an AP supporting the QoS. In the most WLAN environments currently used (for example, WLAN environments in accordance with the IEEE 802.11a/b/g), the non-AP STAs are QSTAs supporting the QoS but the APs are legacy APs not supporting the QoS. As a result, in the WLAN environments currently used, there exists a limitation that even a QSTA cannot utilize the DLS service.
A TDLS (Tunneled Direct Link Setup) is a wireless communication protocol newly suggested to overcome such a limitation regarding the existing DLS service. The TDLS allows the QSTAs to set up a direct link in the currently used WLAN environments in accordance with the IEEE 802.11a/b/g. Accordingly, the TDLS defines methods of allowing the QSTAs to set up a direct link even in the BSS managed by the legacy AP. Hereinafter, a wireless network supporting the TDLS method is referred to as a TDLS wireless network.
In the TDLS wireless network, it is first necessary to specifically define a method of setting up a direct link between two non-AP QSTAs. Particularly, in the TDLS wireless network, an AP does not support the direct link setup method and thus does not directly participate in the setup method of the direct link. Accordingly, there is a need for efficiently and reliably enabling the direct link setup method.
And, in the communication between non-AP QSTAs through the direct link set up, it is necessary to allow the QoS facilities of the non-AP QSTAs to work properly. In addition, when the non-AP QSTAs support High Throughput (HT) capabilities of IEEE 802.11n, it is preferable to allow the HT facilities of the non-AP QSTAs to work properly.